It has long been known to attach an auxiliary sole or slipper onto footwear so as to change the characteristic of the sole of the footwear. Most commonly, the auxiliary device provides additional traction on slippery surfaces such as ice or wet rocks. For ice, such devices frequently employ downward-protruding cleats or caulks to provide greater traction; however, such devices are not effective on wet rocks. One material which has classically been used for providing traction on wet rocks is felt, such as taught in U.S. Pat. No. 3,099,885. Auxiliary felt soles which can be attached to conventional footwear as needed are taught in U.S. Pat. Nos. 1,187,778 and 5,150,536. Auxiliary soles having a cushion material such as felt may also be employed to provide a quieter footstep for hunting or wildlife photography, as taught in U.S. Pat. No. 5,535,529 and U.S. Publication No. 2003/0226281. These auxiliary devices may employ a flat sole portion in combination with a binding structure having a toe-retaining structure and a heel/ankle-retaining structure that serve to secure the sole to the conventional shoe or boot of the wearer, as taught in the '778 patent and in the '281 publication. Alternatively, these devices may employ a moccasin-like structure which wraps around the shoe or boot and is secured by straps or laces, as taught in the '529 and '536 patents. While such devices may be effective for limited use on relatively flat surfaces, such as ice, the bindings may not provide sufficient stability for extended use on inclined surfaces, such as when hiking on rocky terrain. Furthermore, such devices are frequently complicated in structure, making them expensive to fabricate and/or difficult to attach to and detach from the footwear.
Auxiliary soles can also be employed to protect the sole of a boot, such as taught in U.S. Pat. No. 2,801,478, which teaches a protective sole to be attached to a caulked boot such as worn by loggers. The sole both protects the caulks from wear and protects floor surfaces from being damaged by the caulks.
Thus, there is a need for an auxiliary traction device for attachment to a boot or shoe which is simple, compact, and lightweight in structure, yet which attaches readily and securely to the boot or shoe and provides sufficient stability for use on inclined surfaces. With current ski-boot technology, protection of ski boots has become a concern. Since the engagement of the sole of the boot with the binding can affect performance, it is important to avoid wear or damage to the sole of the ski boot. Additionally, since the soles of such boots are typically of stiff, noncompliant material, they provide very little traction. Thus, it is desirable for the sole to be covered when the boot is released from the ski binding. In addition to being easily attachable and detachable, the device for covering the sole should be compact and lightweight so as to be readily carried by the skier.